Two speed gear box for e-cargo bicycles?
- Thread starter Hugh-Jassman
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Chalo
100 TW
gman1971 said:
Index 6-speed hearing has 5.5mm interval spacing. Old 6-speed thumbshifters have a "phantom" click (overshift of the last gear) that can serve as a 7th gear. My guess is that a stack of 7 sprockets at 6-speed spacing would fit nicely on an 8/9/10-speed cassette body, and could be compatible with 1/8" BMX chain. You'd just have to add spacers to the stack to achieve 5.5mm intervals.
Chalo
100 TW
gman1971 said:
More that likely, you'll need to find slightly longer pulley bolts (for instance from an older, wider derailleur).
Chalo,
No need to guess what will work. Just look at the cog and spacer thicknesses listed here, and add them up.
http://www.sheldonbrown.com/cribsheet-spacing.html
Where you run into difficulty making this setup from existing parts is that the OEM cassettes with large cogs ( only 10-11 speed) are all built using spiders for the larger cogs, so it isn't as easy as using thicker spacers. My suggestion would be using cheap 8 speed cassettes
http://www.cambriabike.com/Sunrace-M66-8sp-Cassette-CSM668BV0SS125.asp
for all the cogs but the last one.
http://www.wolftoothcomponents.com/pages/giant-cog
The main downside is that even 7 speed cassettes have only 1.85 mm mm thick cogs, when a BMX chain can handle 3.2 mm thick cogs.
[edit] I just went out in the shed and pulled a NOS Dura-Ace 8 speed cassette out of the box. The cogs are 1.8 mm thick as Sheldon said. Two sandwiched together fit nicely into a new BMX chain. That chain fits nicely into a NOS Shimano 105 derailleur cage.
I would double up 8 speed cogs for all positions but the last one. I'd probably sacrifice a tooth and sandwich two of these together for the last cog.
http://www.ebay.com/itm/MTB-Tools-41-Tooth-Cog-for-Mountain-Bike-Cassette-41t-Sprocket-/261664912556
These cogs doubled up, with two 10 speed spacers between every sandwiched pair of cogs would allow a five speed drivetrain of great strength. You could probably double shift a 10 speed shifter pretty easily,without needing to fill detents.
No need to guess what will work. Just look at the cog and spacer thicknesses listed here, and add them up.
http://www.sheldonbrown.com/cribsheet-spacing.html
Where you run into difficulty making this setup from existing parts is that the OEM cassettes with large cogs ( only 10-11 speed) are all built using spiders for the larger cogs, so it isn't as easy as using thicker spacers. My suggestion would be using cheap 8 speed cassettes
http://www.cambriabike.com/Sunrace-M66-8sp-Cassette-CSM668BV0SS125.asp
for all the cogs but the last one.
http://www.wolftoothcomponents.com/pages/giant-cog
The main downside is that even 7 speed cassettes have only 1.85 mm mm thick cogs, when a BMX chain can handle 3.2 mm thick cogs.
[edit] I just went out in the shed and pulled a NOS Dura-Ace 8 speed cassette out of the box. The cogs are 1.8 mm thick as Sheldon said. Two sandwiched together fit nicely into a new BMX chain. That chain fits nicely into a NOS Shimano 105 derailleur cage.
I would double up 8 speed cogs for all positions but the last one. I'd probably sacrifice a tooth and sandwich two of these together for the last cog.
http://www.ebay.com/itm/MTB-Tools-41-Tooth-Cog-for-Mountain-Bike-Cassette-41t-Sprocket-/261664912556
These cogs doubled up, with two 10 speed spacers between every sandwiched pair of cogs would allow a five speed drivetrain of great strength. You could probably double shift a 10 speed shifter pretty easily,without needing to fill detents.
Chalo
100 TW
The only guesswork is as to whether the chain will bravely coexist with what you wind up with.
Chains wear out sprockets, rather than the other way around. Once a sprocket is badly worn, then it can wreck a chain. So the thickness of the sprocket is much less important than the width of the chain bushing surface.
A narrower sprocket leaves more room for a 1/8" chain to deflect sideways before contacting the adjacent sprocket. So a wider sprocket isn't necessarily an advantage.
Chains wear out sprockets, rather than the other way around. Once a sprocket is badly worn, then it can wreck a chain. So the thickness of the sprocket is much less important than the width of the chain bushing surface.
A narrower sprocket leaves more room for a 1/8" chain to deflect sideways before contacting the adjacent sprocket. So a wider sprocket isn't necessarily an advantage.
Chalo
100 TW
gman1971 said:
Because a chainring can only be aligned with (at most) a single sprocket. When the chain runs to any other rear sprocket, it departs at an angle rather than parallel to the sprocket. That angle uses up clearance between chain and adjacent sprockets.
If you only need two speeds have you considered using a retro-direct type system on the motor output shaft. First put a left hand threaded 1.37x24t freewheel shaft adapter mount fitted with a south paw 24t freewheel on the motor shaft followed by a 30mm right hand thread freewheel with a heavy duty 13t right hand smaller size right hand freewheel mounted. Big 50+ tooth drive sprocket made using an over-sized chain wheel on the wheel or shaft to be driven. Run the chain around the big to be driven big 50+ toother then over to the motor and around the 13t right hand outer sprocket and back to a bearing-ed idler sprocket mounted a little ways away from the motor and around that idler sprocket and back to the motor this time wrapping around the larger south paw freewheel and then back to to connect with the other end of the chain on the other side of the big 50+ tooth.
----- Motor spins CCW it engages the 13t small size freewheel and pulls the chain with it 13t/50+t reduction ratio (AKA=low gear) and the 24t south paw freewheel just freewheels going along with the chain.
----- Motor spins CW it engages the 24t south paw freewheel and pulls the chain with it 24t/50+t reduction ratio (AKA=high gear) and the 13t small size freewheel just freewheels going along with the chain.
Just take a look at the diagram on the wiki page I linked too and envision the big chain wheel on the crank as being what your trying to drive and the motor mounted where the wheel is with the two freewheels one behind the other, one a righty and the other a lefty.
Its possible and its been done before, its how the Xionda and SRAM two speed hub motors work. You just need a controller with drive direction switch reversing leads which becomes a high/low switch instead.
----- Motor spins CCW it engages the 13t small size freewheel and pulls the chain with it 13t/50+t reduction ratio (AKA=low gear) and the 24t south paw freewheel just freewheels going along with the chain.
----- Motor spins CW it engages the 24t south paw freewheel and pulls the chain with it 24t/50+t reduction ratio (AKA=high gear) and the 13t small size freewheel just freewheels going along with the chain.
Just take a look at the diagram on the wiki page I linked too and envision the big chain wheel on the crank as being what your trying to drive and the motor mounted where the wheel is with the two freewheels one behind the other, one a righty and the other a lefty.
Its possible and its been done before, its how the Xionda and SRAM two speed hub motors work. You just need a controller with drive direction switch reversing leads which becomes a high/low switch instead.
Yup. Once you get over 1000 watts you are past current bicycle drive trains and a 2:1, two speed, retro direct makes perfect sense. If you still like to pedal along, like me, run it on the left side, and leave the right side for standard bicycle drive.
Tony01
100 W
Find a 2-speed freewheel. Like this ebay- SUNTOUR-FREEWHEEL-2-SPD-16-20-HOLE-SHOT-BMX-RACE-RACING-cruiser-freestyle-NOS. I think this is your best bet and the lightest too. One of these older 2-sp FWs will let you use heavier duty BMX chain.
Retro direct is cool too.
BUT, do you want engine braking in one gear? If the answer is yes, read on.
I have experience with an auto shift freewheel+clutch 2-speed. For a bike that goes under 40mph this is about the best setup one can ask for (IMO). There is a 3d drawing of one a page or two back in this thread utilizing two input chains/belts with the different ratios; 1st gear driving a FW and 2nd gear driving a cent' clutch.
A word of caution: design your gear reduction carefully. Used as a 2-speed 2nd gear clutch, the minimum shift RPM for a kart clutch happens approximately 2-300rpm later than it is rated for likely because of the heightened load. With a MaxTorque clutch, using the light yellow spring and 6 heavy shoes, the "shift" rpm will happen around 1750rpm (compared to 1500rpm engagement when used on an engine jackshaft). So, if you're running a jackshaft setup with a motor shaft coming out both sides, you'll need to have most of your reduction coming from the jackshaft to the rear wheel in order to keep the RPMs up on the jackshaft to facilitate a shift at a reasonable slow speed. Too much reduction from motor to jackshaft will cause the minimum shift rpm to happen at higher driving speed and will be extremely annoying when you get stuck behind an asian driver who insists on driving *exactly* the 30mph speed limit.
Retro direct is cool too.
BUT, do you want engine braking in one gear? If the answer is yes, read on.
I have experience with an auto shift freewheel+clutch 2-speed. For a bike that goes under 40mph this is about the best setup one can ask for (IMO). There is a 3d drawing of one a page or two back in this thread utilizing two input chains/belts with the different ratios; 1st gear driving a FW and 2nd gear driving a cent' clutch.
A word of caution: design your gear reduction carefully. Used as a 2-speed 2nd gear clutch, the minimum shift RPM for a kart clutch happens approximately 2-300rpm later than it is rated for likely because of the heightened load. With a MaxTorque clutch, using the light yellow spring and 6 heavy shoes, the "shift" rpm will happen around 1750rpm (compared to 1500rpm engagement when used on an engine jackshaft). So, if you're running a jackshaft setup with a motor shaft coming out both sides, you'll need to have most of your reduction coming from the jackshaft to the rear wheel in order to keep the RPMs up on the jackshaft to facilitate a shift at a reasonable slow speed. Too much reduction from motor to jackshaft will cause the minimum shift rpm to happen at higher driving speed and will be extremely annoying when you get stuck behind an asian driver who insists on driving *exactly* the 30mph speed limit.
Hugh-Jassman
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Hugh-Jassman
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a three speed cassette? sounds interesting.
Miles said:
